The primary goal of the proposed research is increased understanding of the interacting environmental and hereditary factors which underlie the normal emmetropization process and which may produce abnormal growth of the eye eventuating in myopia in school-age children. Emerging from consideration of studies of humans and animals is the consensus that retinal defocus is a precursor to the development of myopia. A primary emphasis of the next phase of this research effort is an investigation of factors that induce retinal defocus in children. Some of the factors, such as accommodation, have been studied in the last project period, while others, such as ocular aberrations, are only now being investigated with the advent of new techniques. Genetics studies will investigate what factors may be inherited. Results from this multi-faceted investigation will be combined into an integrated account of myopization. In the process, risk factors for the development of myopia will be identified. The main hypothesis driving this research is that retinal defocus contributes to continued growth of the eye and consequent myopia in susceptible children. The projects as three specific aims: Specific Aim 1: To continue to delineate the time course of development of coordinated accommodation, convergence, and pupillary constriction, and compare it to the onset, progression, and stabilization of myopia. Dynamics of accommodation when children are engaged in near work activities will be investigated, to determine the extent to which retinal defocus may be experienced under conditions which approximate their daily close work habits. The hypothesis to be tested is that children engaged in close work experience retinal defocus that produces myopia. Specific Aim 2: To investigate the role of ocular aberrations, including astigmatism, in the etiology of myopia. Aberrations will be measured under different accommodative demands know to exacerbate aberrations. The hypothesis to be tested is that aberrations degrade retinal images and thereby produce myopia. Specific Aim 3: To complete the collection and ascertainment of a cohort of pedigrees affected by juvenile onset myopia and to begin genetic studies designed to identify genes responsible for overall myopia susceptibility and myopia related specific factors identified in Aims 1 and 2.